Abstract

The scleractinian species Psammocora explanulata and Coscinaraea wellsi were originally classified in the family Siderastreidae, but in a recent morpho-molecular study it appeared that they are more closely related to each other and to the Fungiidae than to any siderastreid taxon. A subsequent morpho-molecular study of the Fungiidae provided new insights regarding the phylogenetic relationships within that family. In the present study existing molecular data sets of both families were analyzed jointly with those of new specimens and sequences of P. expla­nulata and C. wellsi. The results indicate that both species actually belong to the Cycloseris clade within the family Fungiidae. A reappraisal of their morphologic characters based on museum specimens and recently collected material substantiate the molecular results. Consequently, they are renamed Cycloserisex­planulata and C. wellsi. They are polystomatous and encrusting like C. mokai, another species recently added to the genus, whereas all Cycloseris species were initially thought to be monostomatous and free-living. In the light of the new findings, the taxonomy and distribution data of C. explanulata and C. wellsi have been updated and revised. Finally, the ecological implications of the evolutionary history of the three encrusting polystomatous Cycloseris species and their free-living monostomatous congeners are discussed.

Recent molecular studies gave new insights with regard to the phylogeny of the Fungiidae. The encrusting polystomatous species Lithophyllon mokaiHoeksema, 1989 appears to be most closely related to Cycloseris, a genus otherwise consisting of free-living monostomatous species (Gittenberger et al., 2011), whereas based on morphology it was considered a sister taxon of the attached foliaceaous species L. undulatumRehberg, 1892 (Hoeksema, 1989, 1991b, 2009). Furthermore, two encrusting polystomatous species classified with the Siderastreidae Vaughan and Wells, 1943, Psammocora explanulataVan der Horst, 1922 (Fig. 1A-D), and Coscinaraea wellsi Veron and Pichon, 1980 (Fig. 1E-H), appear to be more closely related to one another and to some Fungiidae than to the original congeners. These hypotheses are supported by morphological investigations, which reveal that these two species display typical fungiid skeletal structures which had not been previously noted in these taxa (Benzoni et al., 2007). However, so far these species have not yet been formally revised and their closest relatives among the Fungiidae have remained unknown.

Molecular and morphological hypotheses are often in conflict suggesting that the taxonomic positions of the taxa need to be revised. However, the taxonomic consequences of the genetic results are often not formalized from a taxonomic point of view. The molecular phylogeny of Psammocora explanulata and Coscinaraea wellsi has revealed a taxonomic misplacement, which constitutes a historical constraint as long as they remain in the genus or family to which they were originally assigned based on a misinterpreted morphology. Hence, in lack of a proper study of their type specimens and other collected material, and of supporting field observations, their taxonomic revision stagnates. Therefore, in the present study, the phylogenetic positions of these two species within the Fungiidae are re-examined based on newly obtained mitochondrial COI and nuclear rDNA sequences from material collected throughout the Indo-Pacific and the joint datasets from Benzoni et al. (2007) and Gittenberger et al. (2011). Furthermore, the molecular hypothesis was tested by re-examining the morphological characters of the species in question. Hence, on the basis of the genetic results and of morphological studies, their taxonomic positions are revised. Finally, the study of historical museum material and illustrated specimens allows a reappraisal of their morphologic variability and geographic distribution, which has become increasingly relevant since coral species may have disappeared from areas where they previously occurred (Hoeksema and Koh, 2009; van der Meij et al., 2010; Hoeksema et al., 2011; van der Meij and Visser, 2011).

Material and methods

Sampling

Sampling took place at various localities in the Indo-Pacific (Fig. 2). Specimens were collected for molecular analyses in Egypt (Gulf of Aqaba, Red Sea), Yemen (Gulf of Aden), Socotra Island, Kenya, Mayotte Island, La Réunion, Chagos (Indian Ocean), Indonesia, and New Caledonia (Pacific Ocean). Digital images of living corals in the field were taken with a Canon G9 in an Ikelite underwater housing. Coral specimens were collected, labelled, and fragments of ca 1 cm2 were subsampled and preserved in absolute ethanol for molecular analysis. The remaining corallum was placed in sodium hypochlorite for 48 hours to remove all soft tissue, rinsed in freshwater and dried for microscopic examination. Images of cleaned skeletons were taken with a Canon G9 digital camera.

Type specimens of Psammocora explanulata were examined in the BMNH and ZMA collections. Three of them (BMNH 1937.11.17.116, ZMA Coel. 1072, and ZMA Coel. 1071) are indicated as ‘Syntype’ on their label, while for specimen BMNH 1937.11.17.69 the indication ‘Type’ is given. The holotype of Coscinaraea wellsi USNM 44818 was examined, as well as the specimens of C. wellsi at MTQ that are depicted with the original species description (Veron and Pichon, 1980).

DNA extraction, COI and rDNA amplification and sequencing

Analyses of sequences from the mitochondrial cytochrome c oxidase subunit I gene (COI, partially) and a selection of nuclear rDNA (the entire ITS1, 5.8S, ITS2 and a fragment of 18S and 28S) were used to infer phylogenetic relationships between the examined taxa. COI and rDNA were both amplified from most, but not for all, specimens of Psammocora explanulata and Coscinaraea wellsi analyzed in this study. The list of examined samples and successful amplifications is reported in Table 1. Both markers have been previously used to assess evolutionary relationships among the Anthozoa (Benzoni et al., 2007, 2010; Stefani et al., 2008; Forsman et al., 2009; Gittenberger et al., 2011). The DNA was extracted from ethanol-preserved tissues using a DNeasy® Tissue Kit (QIAGEN, Qiagen Inc., Valencia, CA, USA). Each extract was quantified using a Nanodrop 1000 spectrophotometer (Thermo Scientific).

Table 1. List of specimens from which sequences and morphological data were obtained. For each specimen the code, identification, sampling locality, and Genbank accession code for sequences generated in this study are provided. * For sampling details, see lists of examined material.

Phylogenetic analyses

The obtained COI and rDNA sequences were aligned with other available homologues from the families Siderastreidae and Fungiidae (Benzoni et al., 2007; Gittenberger et al., 2011). In particular all the genera of the former family, and 14 out of 15 of the latter were included in the analyses, thus excluding only the genus CantharellusHoeksema and Best, 1984. Among the 11 species currently recognized in the genus Cyclo­seris, only the six analyzed by Gittenberger et al. (2011) were included in the present analyses. Sequences were viewed, edited and assembled using CodonCode Aligner 2.0.6 (CodonCode Corporation, Dedham, MA, USA). Multiple alignments were finally adjusted using BioEdit 7.0.9.1 (Hall, 1999). Identification of invariable, polymorphic and parsimony informative sites was conducted with DnaSP 5.10.01 (Librado and Rozas, 2009). Intra and interspecific pairwise distances (uncorrected p-distances) were calculated in MEGA 4.0.2 (Tamura et al., 2007).

Phylogenetic relationships were reconstructed using Maximum Parsimony (MP), Maximum Likelihood (ML) and Bayesian Inference (BI). For both markers MP analyses were performed with PAUP* 4.0b10 (Swofford, 2003) using a heuristic search with starting trees obtained by random stepwise addition, with 10 replicates, and the tree bisection-reconnection (TBR) branch swapping algorithm. Bootstrap replicates (n=500) were used to assess the robustness of the internal nodes of the trees. For the ML and BI analyses, nucleotide substitution model parameters were determined by using MrModeltest2.3 (Nylander, 2004). Based on arguments presented by Posada and Buckley (2004), we used the Akaike Information Criterion (AIC) to select best-fit models. The model GTR+I+G (gamma=0.4791 and p-invar=0.4595) was suggested as best fit for COI, and for the rDNA, the model SYM+I+G (gamma=0.6387 and p-invar=0.5340) was selected instead. ML reconstructions were performed with PhyML 3.0 (Guindon and Gascuel, 2003) using the default parameters. The reliability of the ML tree was assessed by bootstrap analyses, with 500 replications. BI analyses were conducted with MrBayes 3.1.2 (Huelsenbeck and Ronquist, 2001; Ronquist and Huelsenbeck, 2003), using the previously determined models of nucleotide evolution. In the case of COI, a Markov Chain Monte Carlo analysis was applied with four chains running for 1,500,000 generations, saving the current tree every 10 generations. Subsequently, a consensus tree was produced (with a burnin of 37500 trees) indicating the Bayesian posterior probabilities of each node. The rDNA phylogeny was obtained on the basis of 6,000,000 generations, sampling trees every 100 generations. The first 30,000 trees were discarded as burnin. Convergence of parameters estimates were monitored using Tracer 1.5 (Drummond and Rambaut, 2007) and by using the statistics provided by MrBayes.

Results

COI phylogeny

Seven COI sequences for Coscinaraea wellsi and five for Psammocora explanulata were obtained. All sequences for Coscinaraea wellsi except the one from Ternate, Indonesia, shared the same haplotype. After alignment, 455 base pairs were obtained for the COI fragment, containing 329 invariable, 17 uninformative, and 109 parsimony informative base pairs with a total of 170 mutations. No indels were detected. Galaxea fascicularis (clade V and Complex group) was selected as outgroup due to its divergence from Siderastrea (clade IX and Complex group) and clade XI (Robust group) based on the mitochondrial tree proposed by Fukami et al. (2008).

All phylogenetic methods (BI, MP, ML) provided trees with the same overall topology, i.e. all specimens were assigned to the same clades, and the relationships among these clades were stable (Fig. 3). Siderastrea de Blainville, 1830, the type genus of the family Siderastreidae, is highly divergent from the other Siderastreidae (sensuVeron, 2000) as already shown in previous molecular studies (Benzoni et al., 2007; Fukami et al., 2008; Kitahara et al., 2010). The genera Coscinaraea Milne Edwards and Haime, 1848, Psammocora Dana, 1846, Horastrea Pichon 1971, and AnomastraeaMarenzeller, 1901, form a strongly supported group including the Siderastreidae and Psammocoridae clades in Fig. 3. This, together with the Fungiidae and the genera Oulastrea Milne Edwards and Haime, 1848, and LeptastreaMilne Edwards and Haime, 1848 (both traditionally ascribed to the Faviidae) form a larger and well supported clade (Fig. 3). All the taxa in this larger clade were assigned to clade XI by Fukami et al. (2008). However, in our analysis Oulastrea crispata (Lamarck, 1816) appears to be highly distinctive and basal to the remainder of this clade (Fukami et al., 2008). Two main subclades are evidenced in clade XI. One subclade comprises the remaining siderastreids, with the exception of C. wellsi and P. explanulata. The other subclade includes all fungiids, all specimens of C. wellsi and P. explanulata, and Leptastrea. Moreover, C. wellsi and P. explanulata are closely related to each other together with the genera CycloserisMilne Edwards and Haime, 1849 and Pleuractis Verrill, 1864. This group is also well supported by different phylogenetic analyses (posterior probability=99, MP bootstrap=88, ML bootstrap=83). The close relationships between C. wellsi and P. explanulata among the Cycloseris species are also supported by pairwise distances. The genetic distance of C. wellsi and P. explanulata compared to the Cycloseris species is very low (0.1 ± 0.04% in both cases). Conversely, significantly higher values are evidenced between C. wellsi and its congeners Coscinaraea monile (Forskål, 1775) (3.1 ± 0.8%) and C. columna (Dana, 1846) (3.0 ± 0.8%), and between P. explanulata and the other Psammocora species (3.9 ± 0.8%).

Fig. 3. Phylogenetic tree based on the mitochondrial gene COI inferred by Bayesian inference. The clade support values are a posteriori probabilities transformed to a percentage (BI), bootstrap values from maximum parsimony (MP) and bootstrap values from maximum likelihood (ML), in this order. Sequences generated in this study are in bold.

rDNA phylogeny

A total of eight sequences of C. wellsi and six of P. explanulata were obtained for the rDNA locus. Direct sequencing produced reliable electropherograms and no ambiguous nucleotide peaks. The aligned matrix was 678 base pairs long, 419 positions were constant, 128 positions were polymorphic, and 64 base pairs potentially parsimony-informative. Finally, 127 indel sites were found, and they were treated as a fifth character in phylogenetic analyses. Oulastrea crispata was selected as outgroup owing to its high divergence within clade XI sensuFukami et al. (2008) based on mitochondrial phylogeny (Fig. 3), and because sequences from other outgroups were not available for this marker.

The general topology of the phylogeny reconstructions obtained with MP, ML and Bayesian procedures was congruent (Fig. 4), with minor differences in the relationships among sequences in the terminal clades and reflecting the same topology as observed in COI phylogeny.

Fig. 4. Phylogenetic tree based on rDNA (spanning the entire ITS1, 5.8S, ITS2 and a portion of 28S and 18S) inferred by Bayesian inference. The clade support values are a posteriori probabilities transformed to a percentage (BI), bootstrap values from maximum parsimony (MP) and bootstrap values from maximum likelihood (ML), in this order. Sequences generated in this study are in bold.

Two main subclades within clade XI sensuFukami (2008) are partially recognizable. Coscinaraea columna (Dana, 1846) and Psammocora contigua (Esper, 1794) form a well-supported group, separated from C. wellsi and P. explanulata. The average distance of C. wellsi from C. columna is 5.5 ± 0.9%, while genetic divergence between P. explanulata and P. contigua is 5.0 ± 0.8%. Thus, even in this case, the two species are distantly related to their supposed congeners. The Fungiidae and C. wellsi and P. explanulata form an unresolved clade due to a large basal polytomy. Nevertheless, all monophyletic groups represented by more than one species are the same as those recovered in the nuclear phylogeny of Fungiidae by Gittenberger et al. (2011) and therefore not discussed again. All the examined specimens of C. wellsi and P. explanulata are in a well-supported group including Pleuractis gravis (Nemenzo, 1955), P. spec. 1 and all Cycloseris species. These two species show a close phylogenetic relationship to Cycloseris, as corroborated by average distances between C. wellsi and Cycloseris (1.4 ± 0.4%) and between P. explanulata and Cycloseris (1.7 ± 0.4%). C. wellsi and P. explanulata form two resolved but not monophyletic lineages due to the presence of Cycloseris sinensisMilne Edwards and Haime, 1851 in the C. wellsi clade, and of Cycloseris costulata (Ortmann, 1889) in the P. explanulata clade.

A reappraisal of the morphology and distribution of Cycloseris explanulata and of C. wellsi is given in the Appendix. Based on the aforementioned molecular evidence and morphologic observations discussed hereafter, the taxonomic position of the two species is revised and both are formally assigned to the genus Cycloseris within the family Fungiidae.

Discussion

Phylogeny, taxonomy, and distribution of Cycloseris explanulata and Cycloseris wellsi

The joint analyses of the databases of Benzoni et al. (2007) and Gittenberger et al. (2011), and the study of a large collection of specimens of Cycloseris wellsi and C. explanulata (Appendix) confirmed that both species are genetically and structurally more related to each other and to the Fungiidae than to Coscinaraea or Psammocora, the genera to which they originally belonged, respectively (Benzoni et al., 2007). Both species share typical structural characters typical for the Fungiidae (i.e. interstomatous septa, tentacular lobes, fulturae) and which are not found in any other of the taxa ascribed to the Siderastreidae. Conversely, they lack typical structures found in the genera to which they were originally assigned. For example, in both Cycloseris wellsi and C. explanulata the structure of the colony wall is septothecal, the septa are joined by fulturae, and the costae developed, whereas in Psammocora and Coscinaraea the corallum wall is synapticulothecal, the septa are joined by synapticulae and costae are not developed (Benzoni et al., 2007). Furthermore, both these attached and polystomatous taxa share a combination of morphologic characters that are typical of Cycloseris, i.e. a solid corallum wall, the presence of fine and sharp septal margin and lateral septa ornamentation, and of costae covered by fine protuberances (Hoeksema, 1989). Moreover, both the mitochondrial (Fig. 3) and the nuclear marker (Fig. 4) indicate that among the fungiids C. wellsi and C. explanulata are most closely related to species in the monophyletic genus Cycloseris. In particular, all examined specimens of C. wellsi were recovered in the same clade as Cycloseris cyclolites (Lamarck, 1816), the type species of the genus. The phylogenetic trees in Figs. 3 and 4 show complementary information with no conflicting signals. Indeed no species or species groups are found in different or contrasting clades. The only differences concern the resolution of some species groups detected in COI rather than in rDNA trees. In general, the COI phylogenies resolve evolutionary relationships at a more basal taxonomic level detecting four well-supported clades in these corals, namely the Siderastreidae (Complex clade), Sidera­streidae (Robust clade), Psammocoridae, and Fungiidae clades. This is in agreement with the well known slow substitution rate of COI in corals (Hellberg, 2006; Huang et al., 2008). On the contrary, rDNA phylogeny does not recover the monophyly of Fungiidae clade but it is useful to investigate phylogenetic relationships at genus and species level within this clade. While in the mitochondrial cladogram Psammocora explanulata and Coscinaraea wellsi are grouped together with no genetic differentiation in the mitochondrial tree (Fig. 3), in the rDNA cladogram the position of these two species is well-resolved (Fig. 4) due to the higher resolution of ITS1 and ITS2 regions (Chen et al., 2004; Wei et al., 2006).

Despite having been traditionally assigned to two different genera, C. wellsi and C. explanulata are morphologically very similar (Veron and Pichon, 1980; Veron, 2000) (Figs. 1, 6, 8). In the taxonomic literature the former species has been confused with the latter (see the synonymies above) and one of the ‘syntypes’ of C. explanulata (ZMA Coel. 1071, Fig. 8F) is actually a specimen of C. wellsi (cf. UNIMIB KE 404, Fig. 8E). This is not surprising considering the morphological similarity and the co-occurrence of both species in similar environments (also shared with C. mokai) and their overlapping wide Indo-Pacific distribution ranges (Figs. 7 and 9). This being said, C. wellsi has larger calices, more septa reaching the fossa, longer and more winding interstomatous septa, and longer enclosed petaloid septa. Finally, in daytime C. explanulata tentacles are mostly extended (Fig. 1A-D) whilst C. wellsi polyps are mostly retracted (Fig. 1E-H).

On the basis of the examined material, the known geographic distribution ranges of C. explanulata and C. wellsi are updated and extended when compared to those presented by Veron (2000). The distribution ranges of both species show much overlap, extending from eastern Africa and the Red Sea to Hawaii and French Polynesia (Figs. 7, 9). New records for C. wellsi are from the Gulf of Aden (Djibouti and Socotra Island) Kenya and French Polynesia and for C. explanulata from Vietnam, the Line Islands, and New Caledonia (Appendix).

Attached and polystomatous Cycloseris species

Attached species among the Fungiidae appear to be more common than previously assumed (Hoeksema, 1989, 2009). They belong to the genera Cantharellus, Lithophyllon, Podabacia, and Cycloseris (Gittenberger et al., 2011). The phylogenetic and taxonomic position of Cantharellus with three small monostomatous species is uncertain but it is probably closely related to Cycloseris (Hoeksema, 1989; Gittenberger et al., 2011). The genera Lithophyllon and Podabacia consist of polystomatous species, which are foliaceaous and may attain large sizes (Hoeksema, 1989, 1991b, 2009). With the present inclusion of C. explanulata and C. wellsi in the Fungiidae, the number of ten attached species among 50 mushroom coral species (Gittenberger et al., 2011) has increased to 12 among 52.

The earlier inclusion of the encrusting polystomatous species C. mokai in Cycloseris by Gittenberger et al. (2011) was unexpected because Cycloseris originally used to consist of free-living monostomatous species. Specimens of C. mokai are usually found in lower reef slope habitats, mostly above sandy bottoms, where they live attached to the vertical sides of rocks, which may help to prevent burial (Hoeksema, 2012a). The possession of multiple mouths may spread the risk of mouth clogging and feeding obstruction in conditions of heavy sedimentation (Hoeksema, 1991b). From a phylo-ecological perspective, C mokai may be derived from an ancestor that lived on sediment but because it lost the capacity to detach itself (a morphological or life history character state reversal), its vertical distribution range became shallower (an ecological character state reversal) (Hoeksema, in prep.).

Cycloseris explanulata and C. wellsi belong to separate lineages within Cycloseris (Figs. 4 and 5) and their ancestors may have undergone a similar fate as those of C. mokai. According to the present phylogeny reconstruction it appears that all three species had free-living ancestors that lived on sandy substrates in the proximity of lower reef slopes, where they may have settled as planula larvae (see e.g. Hoeksema, 2012a). Moreover, the three species belong to three separate lineages within the genus Cycloseris, each comprising both attached and polystomatous species in addition to free-living and monostomatous corals (Fig. 5). The three attached Cycloseris species are usually small and have many mouths in close proximity to each other, which may be an advantage in conditions of limited substratum surface (Hoeksema, 1991b). The present scenario confirms that homoplasy (convergence), including character reversals from both morphological and ecological perspective, is a common phenomenon among mushroom corals (Hoeksema, 1991b; Gittenberger et al., 2011).

Fig. 5. Detail of the rDNA phylogeny showing the Cycloseris clade (highlighted in grey in Fig. 3) modified to indicate the presence of attached and polystomatous species and free-living and monostomatous species in each of its main lineages (I – III). A) Cycloseris mokai, Prony Bay, New Caledonia, new geographic record (image from the IRD Nouméa Lagplon archive); B) C. tenuis, Sulawesi, Indonesia (photo BWH); C) C. explanulata, Mayotte Island; D) C. costulata, Bali, Indonesia (photo BWH); E) C. wellsi, Bali, Indonesia (photo BWH); F) C. sinensis, Banc Gail, New Caledonia (image from the IRD Nouméa Lagplon archive). Black squares indicate attached and polystomatous taxa, white squares free-living and monostomatous ones. Please note that letters placed after the squares in the tree on the left hand side of the figure correspond to the photo labels on the right hand side.

The present study confirms the utility of re-examining morphological characters in the light of new molecular data as already demonstrated by previous studies (e.g. Budd and Stolarski 2009, 2011; Benzoni et al., 2011). This allowed the re-assignment of two misclassified mushroom corals to the family Fungiidae, based on the re-examination of historical museum material and analyses of new specimens with DNA samples recently collected by the authors (e.g. Djibouti, Kenya, the Line Islands, New Caledonia, Sabah, Yemen). This confirms that historical and new collections of skeletons and DNA are of paramount importance for the development of our knowledge of the diversity, phylogeny, and biogeography of hard corals and other marine organisms (Hoeksema et al., 2011; Karsenti et al., 2011).

Acknowledgements

The authors are grateful to three anonymous reviewers for constructive critics on the manuscript. We wish to thank D. Obura (CORDIO) for sampling in Kenya and in Chagos. Specimens in New Caledonia were collected for this study thanks to the help of C. Payri (IRD Noumea), G. Lasne, J.L. Menou, J. Butscher, E. Folcher and the RV Alis captain and crew. We thank Michel Pichon (MTQ) and Yannick Geynet (IREMIA) and the Corail Plongée staff for assistance with sampling in La Réunion; E. Dutrieux (CREOCEAN), C.H. Chaineau (Total SA), R. Hirst and M. AbdulAziz (YLNG), M.A. Ahmad and F.N. Saeed (EPA Socotra), C. Riva, A. Caragnano (UNIMIB), and S. Basheen (Professional Divers Yemen) in Yemen; M. Fouda and K.A. Harhash (EEAA), all the Ras Mohammed National Park staff, Y. Khalifa and the Albatros Top Diving staff in Egypt. Sampling in Djibouti was possible thanks to the Tara Oceans scientific expedition and the OCEANS Consortium and to the collaboration of A.O. Dini (l’Aménagement du Territoire et de l’Environnement de Djibouti), M. Jalludin and M. Nabil (CERD) and J-F. Breton (IFAR Djibouti). We are grateful in particular to E. Karsenti (EMBL) for allowing reef research during the expedition, O. Quesnel, S. Kandels-Lewis (EMBL), and Captain O. Marien and the Tara crew in general, and to M. Oriot and S. Audrain in particular. We are also indebted to R. Friederich (World Courier) and R. Troublé (Fonds Tara). The O6 team support is greatly acknowledged. We are grateful to UNIMIB Lab 2014 and to Diego, Daniela, and Andrea in particular for allowing use of the Nanodrop 1000 spectrophotometer, and to E. Reynaud (Adéquation & Développement) for kindly donating part of the UNIMIB laboratory instruments for this study.

Hoeksema BW. 1991a. Control of bleaching in mushroom coral populations (Scleractinia: Fungiidae) in the Java Sea: stress tolerance and interference by life history strategy. Marine Ecology Progress Series 74: 225-237.

Hoeksema BW. 2009. Attached mushroom corals (Scleractinia: Fungiidae) in sediment-stressed reef conditions at Singapore, including a new species and a new record. Raffles Bulletin of Zoology Supplement 22: 81-90.

Morphology. Animals polystomatous. Corallum attached, generally thinly encrusting and following the underlying substrate (Fig. 1A-D). Colonies irregular in outline although smaller colonies can be circular (Fig. 1A). Calices scattered over the corallum surface without any particular arrangement (Fig. 6), they can be more closely packed (Fig. 6D) or more distant (Fig. 6B). Calice diameter between 2.6 and 3.1 mm. Thicker and more exsert septa (five to seven) alternate with thinner septa flush with the corallum surface. The former are mostly petaloid in shape (Fig. 6). Continuous septa going from one fossa to the other between adjacent calices, previously referred to as septocostae (Van der Horst, 1921, 1922; Veron and Pichon, 1976), can be observed in some specimens (Fig. 6A-D; Veron and Pichon, 1976, Figs 28, 31-32). These are actually interstomatous septa (Benzoni, 2007) homologous to those found in the Fungiidae (sensuHoeksema, 1989). Enclosed petaloid septa derived from the alternate fusion of lower and higher order septa are found between calices like in the genus PsammocoraDana, 1846 (Benzoni et al., 2007, 2010). They range from 1.4 to 1.7 mm in length (Benzoni, 2007). Morphologic affinities between the pattern of septa fusion in C. explanulata and in the fungiid genus PolyphylliaBlainville, 1830 have been remarked by Van der Horst (1922) in the original species description. While enclosed septa with a petaloid outline are always observed in C. explanulata, interstomatous septa are developed in some specimens (Fig. 6E-H), and are mostly found between closely neighboring corallites (Veron and Pichon, 1976, Figs 31-32), i.e. less than one calice away from each other. Exsert tentacular lobes are typically found on top of thicker septa and enclosed petaloid septa in this species (Fig. 6). Septal margins are ornamented by ridges composed of short series of minute granules oriented transversally to the septal plane forming distinct septal paddles (Benzoni et al. 2007, Fig. 3G). Septal sides are ornamented by minute granules. Septa in C. explanulata are connected by buttress-like structures developing below the septal edge and joining the septa sides (Benzoni et al. 2007, Fig. 5B). These structures defined as fulturae are typical for the Fungiidae (see Gill, 1980, pl.1:1 for FungiaLamarck, 1801; Hoeksema, 1989, Fig. 652 for HerpolithaEschscholtz, 1824; Fig. 656 for SandalolithaQuelch, 1884; Fig. 664 for LithophyllonRehberg, 1892). Fulturae differ from the synapticulae found, inter alia, in the Siderastreidae which are typically isolated from each other and are often developed near the septal edge (Gill, 1980). Columella always present, papillary, and formed by six to 15 tightly packed vertical processes all of the same size (Fig. 6H). Colony wall septothecal and compact. Costae are found on the lower side of the corallum, they are small and ornamented by minute rounded granulations. Unfortunately, they are often obscured due to the attached growth mode, and by the incrustations of crustose coralline algae and invertebrates. These are small and ornamented by minute rounded granulations.

Geographical distribution. Cycloseris explanulata occurs throughout the Indo-Pacific. Based on the present material and published illustrations it is recorded from Egypt, Saudi Arabia, Yemen, Socotra Island, Maldives, Chagos, Seychelles, Mayotte, Madagascar, La Réunion, Thailand, Indonesia, Vietnam, Papua New Guinea, Australia, New Caledonia, the Marshall Islands, Hawaii, the Line Islands, and French Polynesia (Fig. 7).

Morphology. Animals polystomatous. Corallum attached (Fig. 1E-H). Colonies are encrusting and with a circular or oval outline (Fig. 1E-F), their margins sometimes detached from the substratum (Fig. 1E, G). Calices scattered over the corallum surface or in a serial arrangement especially towards the margins (Fig. 1F, G; Fig. 8). Calice diameter between 3.5 and 5.1 mm. Septa unequal and alternating, thicker septa may be more exsert than thinner ones (Fig. 8C). Six to 10 thicker septa may reach the fossa (Fig. 8). Interstomatous septa between calices up to 1.3 calices away from each other. In some corallites all septa reaching the fossa can be interstomatous (Fig. 8G). Elongated enclosed petaloid septa running parallel to interstomatous septa over the corallum surface are also commonly observed. These can be short and straight (Fig. 8C-E) or long and attain irregular shapes (Fig. 8H). Exsert tentacular lobes are typically observed on top of thicker septa and of enclosed petaloid septa, and at both ends of interstomatous septa in the holotype and in many specimens (Fig. 8B-C). However, they can be reduced and barely visible in other specimens (Fig. 8D-F). Septal margins are ornamented by septal paddles (Benzoni et al., 2007, Fig. 4B). Septal sides are ornamented by minute granules. Septa in C. wellsi are connected by fulturae (Benzoni et al., 2007, Fig. 5C). Columella always present, papillary, and formed by nine to 21 tightly packed vertical processes of equal size (Fig. 8H). Colony wall septothecal and compact, ornamented by fine costae (Veron and Pichon, 1980). Costae in C. wellsi and their ornamentation are very similar to those of Lithophyllon mokai (Hoeksema, 1989: Fig. 594).

Distribution. Cycloseris wellsi occurs throughout the Indo-Pacific. Based on the present material and published illustrations C. wellsi has been recorded from Egypt, Djibouti, Yemen, Socotra Island, Kenya, Seychelles, Mayotte, La Réunion, Thailand, Indonesia, Vietnam, Malaysia, Philippines, Taiwan, Japan, Papua New Guinea, Australia, New Caledonia, Hawaii, and French Polynesia (Fig. 9).